Conventional pump dispensers typically comprise an assembly of several separate components, including a tubular body defining an interior pumping chamber, a collar which is assembled onto the upper end of the body, and a reciprocal plunger which is received within the body and slides through the collar during operation. Normally, the collar is snap-fitted onto the body using circular beads and grooves which matingly interengage and thus prevent the collar from accidentally pulling free of the body in an axial direction.
Such snap beads and the like are quite adquate insofar as avoiding axial displacement of the collar is concerned, but it has been found that with the advent of down-locking plungers, in which lugs of the plunger may be selectively locked under overhanging structure on the collar, the collar may have a tendency to rotate relative to the body during the locking and unlocking operations, thereby inhibiting the relative rotation between the plunger and collar which is necessary to effectively complete the locking and unlocking movements.
Various attempts have been made to remedy this situation through increasing the interference fit between the collar and body in a radial direction so that the collar is simply more tightly engaged with the body. However, such approaches have not been successful to the desired degree, and thus there is a significant need for a simply, yet effective way of solving this problem.